Light pulse induces ALA-S gene expression in the rat Harderian gland.

The rodent Harderian glands (HGs) are large paired orbital organs with highest porphyrinogenic rates. We have previously shown that continuous light exposure abolished the day/night variations of the delta-aminolevulinate synthase (ALA-S; the rate-limiting enzyme for porphyrin biosynthesis) gene expression observed under standard light: dark cycles (LD 12:12) in the rat HGs. This study was designed to examine whether the ALA-S changes were actually associated directly with light. The response of ferrochelatase (enzyme that converts protoporphyrin IX into heme) to light was also examined. Male Wistar rats were acclimatized to light: dark cycles regimen of 12:12 for 2 weeks. At the end of the 2 weeks, a 1 h-light pulse was applied in the middle of the dark phase. Animals were sacrificed immediately after the end of the light pulse. HGs were collected and stored at -80 degrees C until processed for quantitative RT-PCR. A 1 h-light pulse applied during mid-dark caused a significant increase of ALA-S gene expression (3-fold higher than in controls), whereas it was without effect on ferrochelatase gene expression. Our results suggest that light per se may regulate ALA-S gene expression in the rat HGs, and reveal that the ALA-S gene expression, and so heme biosynthesis, is under a photodynamic control.

Pineal system of desert rodents and its relationship to the epithalamus.

The morphological relationships of the pineal complex to the epithalamic structures have been examined at light microscopic level in five desert rodent species, Meriones crassus, Meriones lybicus, Gerbillus gerbillus, Psammomys obesus and Ctenodactylus vali. The pineal complex is classified as type ABC in M. crassus and G. gerbillus, AC in M. lybicus, AbetaC in P. obesus and alphabetaC in C. vali. In these rodent species, the pineal is an elongated organ which is dumbbell-shaped in G. gerbillus and M. lybicus, and extends above the cerebral hemispheres in M. crassus, leaf-shaped in P. obesus and lancet-shaped in C. vali. In P. obesus, pigment-containing cells are noted in the superficial part of the gland. In all species examined, the suprahabenular recess which is an extension of the choroid plexus of the third ventricule establishes a close anatomical relationship with the deep pineal. In C. vali, the suprahabenular recess is also contiguous with the pineal stalk and the superficial pineal component. In M. lybicus, M. crassus, G. gerbillus and P. obesus, a prominent dorsal vessel, the vena cerebri magna, intervenes between the suprahabenular recess, the superficial portion and the stalk. The most striking feature noted in this study is the presence of numerous melanocytes in the connective tissue capsule of the pineal gland, in the connecting stalk and in the connective tissue core of the highly convoluted suprahabenular recess in M. lybicus and M. crassus. The location of melanocytes in the restricted pineal area may suggest that these cells have a morphosignificance in photoreception or photoprotection.

A clinicomycological study of fungal foot infections among Algerian military personnel.

There have been few studies on fungal infection of the foot in military personnel. The aim of this study was to determine the prevalence and aetiological factors of superficial mycoses of the foot in military personnel attending the Department of Dermatology of the Army Central Hospital in Algiers, Algeria. A complete dermatological examination was performed in 650 male military personnel. Cultures of skin and nail specimens of the feet were performed for each participant. Fungal infection of the foot (including tinea pedis and Candida interdigital infection) was clinically diagnosed in 147, and confirmed in 119 by positive cultures, resulting in a total prevalence of 18.3%. When subjects were grouped according to military rank, fungal infection of the foot was prevalent in troop soldiers; when grouped according to years of service to the army, the infection was frequent in military recruits. The dermatophyte species Trichophyton rubrum (20.9%) and the yeast species Candida parapsilosis (18.7%) were shown to be the major causal agents isolated. Tinea pedis and Candida interdigital infection are the most prevalent (68%) superficial fungal infections among Algerian military personnel.

Effect of a synthetic pineal tetrapeptide (Ala-Glu-Asp-GLy) on melatonin secretion by the pineal gland of young and old rats.

The pineal gland contains many peptides known to be implicated in melatonin production. We examined the effects of a synthetic pineal tetrapeptide Ala-Glu-Asp-Gly on melatonin secretion by the pineal gland. The tetrapeptide effects on pineal gland melatonin secretion were studied in young (9 weeks) and old (27 months) male Wistar rats using a perifusion device. Pineal tetrapeptide at the concentrations used (10(-4) to 10(-6) M) had no significant effect upon melatonin secretion whatever the age of the animals, young or old. We also looked at the effect of the tetrapeptide on pineal melatonin stimulated by a beta-adrenergic agonist, isoproterenol. We found that isoproterenol-induced melatonin increase was not modified by the tetrapeptide. Our results suggest that the pineal tetrapeptide Ala-Glu-Asp-Gly, does not seem to play a role, at least in vitro, in the control of melatonin secretion by the rat pineal gland.

The Harderian gland in diabetic sand rats (Psammomys obesus) a light microscopic study.

The purpose of this study was to examine the long-term effects of synthetic diet on the sand rat Harderian gland. From the third month, animals showed a diabetic syndrome characterized histologically by Harderian gland necrotic changes. Some gland tubules and melanocytes were disintegrated and numerous mast cells were densely populated in the connective capsule of the gland. Moreover, luminal porphyrin accretions and cellular debris were often associated with alcian blue positive materials. If the synthetic diet lasted more than 6 months, the gland was strongly damaged and numerous plasma cells, macrophages, and lymphocytes infiltrated the gland. These results clearly demonstrate that the sand rat Harderian gland is affected by the diabetic syndrome induced by the synthetic diet.

Chronic diazepam administration differentially affects melatonin synthesis in rat pineal and Harderian glands.

RATIONALE: Pineal and Harderian gland melatonin production as well as plasma melatonin levels were investigated in male Wistar rats (12 weeks old) after administration of diazepam, a benzodiazepine widely used as anxiolytic. OBJECTIVE: The present study investigates the effects of a chronic administration of diazepam on pineal and Harderian gland melatonin contents. METHODS: Diazepam was administered subcutaneously, for 21 days, at a dosage of 3 mg/kg body weight per day, 1 h before the onset of darkness. RESULTS: Diazepam clearly affected pineal melatonin biosynthesis and plasma melatonin levels. Diazepam reduced the pineal melatonin content (by a factor of 2) and the activity of N-acetyltransferase (NAT) (by a factor of 3.5), as well as plasma melatonin levels (by a factor of 1.5), but had no effects on pineal hydroxyindole-O-methyltransferase activity. By contrast to the pineal gland, diazepam failed to affect the Harderian gland melatonin content. CONCLUSIONS: Our results suggest that the inhibition of melatonin production induced by diazepam in vivo may be due to a direct action of this benzodiazepine on the pineal gland, through its action on NAT, the key enzyme of melatonin synthesis, and that the control of melatonin production in the Harderian glands may be different from that observed in the pineal gland.

Melatonin synthesis in the rat harderian gland: age- and time-related effects.

The Harderian gland is considered as an extrapineal source of melatonin. In the pineal gland, melatonin is known to present a circadian rhythm with high concentration during nighttime in all species studied. We determined in Wistar male rats the effects of age and time of day on melatonin synthesis in the Harderian gland. We compared Harderian gland melatonin content and the hormone synthesizing enzymes, serotonin N-acetyltransferase and hydroxyindole-O-methyltransferase, in young (4 months) and old (22 months) animals at six circadian stages and found that melatonin synthesis in the Harderian gland was unaffected by age. We also studied the Wistar rat Harderian gland at ten different circadian stages and found that the Harderian gland did not exhibit a daily rhythm in its melatonin content. This study shows that, by contrast to the pineal gland, melatonin in Wistar rat Harderian gland does not exhibit daily variations and that aging does not affect the melatonin content of the gland.

Long-term daily melatonin infusion induces a large increase in N-acetyltransferase activity, hydroxyindole-O-methyltransferase activity, and melatonin content in the Harderian gland and eye of pinealectomized male Siberian hamsters (Phodopus sungorus).

The effects of long-term daily melatonin infusions on the melatonin synthetic pathway in the Harderian glands and eyes of male Siberian hamsters were studied. Hamsters were pinealectomized (PX) and infused daily for 8 hr with either melatonin (6 microg/hr) or vehicle for 7 days in short photoperiod (SP, 10L:14D), followed by 14 wk in either SP (SP group) or in constant darkness (DD group). After the infusion period (15 wk), the infusion was stopped and animals were transferred into SP for 3 wk. The hamsters were then killed at midday or midnight. Exogenous melatonin infusion caused an increase in the Harderian gland weight, which was still evident 3 wk after the end of the treatment. In addition, exogenous melatonin increased endogenous melatonin concentrations (4-fold) and hydroxyindole-O-methyltransferase (HIOMT) activity (2-fold). N-acetyltransferase (NAT) activity, however, was not increased, and no day/night difference in melatonin content and HIOMT activity was observed in the Harderian glands. In the eye, melatonin infusions significantly increased day and night-time melatonin levels (up to 3-fold) and both NAT and HIOMT activities (up to 3.5-fold). This effect of melatonin treatment was observed in both SP and DD groups. These observations demonstrate that exogenously-infused melatonin at relatively high doses activates the synthesis of endogenous melatonin in the Harderian gland and eye of the Siberian hamster. Circulating levels of melatonin were also markedly increased, indicating that in these conditions melatonin may be released from extra-pineal sites.

Immunohistochemical evidence for the presence of tryptophan hydroxylase and serotonin in the rodent Harderian gland.

The Harderian gland is considered as being an extrapineal source of melatonin. In most rodents, the Harderian gland contains two epithelial cell types (I and II). The aim of this study has been to define which cell type is involved in indoleamine synthesis. The presence and localization of serotonin (melatonin precursor) and tryptophan hydroxylase (the rate-limiting enzyme for serotonin synthesis) have been investigated by immunohistochemistry in male Wistar rats, Syrian hamsters and Djungarian hamsters. The results of the present study show that immunoreactivity for tryptophan hydroxylase and serotonin is confined to the type I cell, suggesting that this cell type is involved in indoleamine synthesis in the rodent Harderian gland.

Immunohistochemical characterisation of epithelial cells of rodent harderian glands in primary culture.

The aims of the current investigation were (1) to establish an efficient procedure for the isolation of rodent harderian gland cells and to define conditions for maintenance of viable differentiated cells; (2) to compare the in vitro growth pattern of cultured epithelial cells; and (3) to characterise the cultured epithelial cells from 3 rodent species: Wistar rats, Syrian hamsters and Djungarian hamsters. We have established primary culture conditions that permit the maintenance of viable and differentiated secretory cells from adult rodent harderian gland. This study demonstrates that the cell growth pattern is faster in hamsters than in rats and despite morphological changes, epithelial cells reestablish their distinctive (biochemical/metabolic) phenotype as indicated by lipid-containing vacuoles, porphyrin pigment and serotonin and tryptophan hydroxylase labelling.

Evidence for melatonin synthesis in rodent Harderian gland: a dynamic in vitro study.

Melatonin content and release from Harderian glands (HGs) has been measured by an in vitro perifusion technique in three rodent species: Wistar rat, Syrian hamster, and Siberian hamster. Melatonin immunoreactive concentrations in HGs of animals killed at 10.00 hr were 0.31 +/- 0.031 pg/mg gland in male Wistar rat, 0.54 +/- 0.026 pg/mg gland in male Siberian hamster, 0.17 +/- 0.070 and 0.20 +/- 0.059 pg/mg gland in male and female Syrian hamster, respectively. In all species examined, isolated HGs perifused for 9-15 hr released melatonin but did not stabilize their melatonin release rate. No sex-related difference could be noted in the HG melatonin release rate. The total amount of melatonin released over a 15 hr long perifusion was about 0.075 +/- 0.004 ng/15 h/mg gland and 0.063 +/- 0.010 ng/15 hr/mg gland in male and female Wistar rat, respectively; 0.155 +/- 0.019 ng/15 hr/mg gland and 0.141 +/- 0.006 ng/15 hr/mg gland in male and female Siberian hamster, respectively; 0.035 +/- 0.003 ng/15 hr/mg gland and 0.045 +/- 0.004 ng/15 hr/mg gland in male and female Syrian hamster, respectively. This amount, which is higher than the tissue levels, demonstrates the de novo melatonin synthesis. This is confirmed by the fact that infusion of the indoleamine precursor, tryptophan (TRP), stimulated melatonin secretion from HGs. The melatonin release is increased by 2.5-fold in male and female Wistar rat, 1.5-fold in male and female Siberian hamster, and 2.0- and 3.0-fold in male and female Syrian hamster, respectively. Treatment with a TRP hydroxylase inhibitor, para-chlorophenylalanine, reduced basal melatonin release and inhibited the TRP-induced melatonin stimulation. Kinetics and amounts of melatonin released were not affected by pinealectomy, ruling out a possible plasmatic origin of the HG melatonin. Isoproterenol, a beta-adrenergic agonist, and dibutyryl cyclic AMP, a cyclic AMP analogue, failed to stimulate HG melatonin secretion. In conclusion, these results confirm the presence of melatonin in the HGs and demonstrate that melatonin is synthesized in and released from isolated rodent HGs.

Comparative histological and ultrastructural studies of the Harderian gland of rodents.

The Harderian glands of six rodents (the Wistar rat, the gerbils Psammomys obesus, Gerbillus gerbillus, Meriones crassus, and Meriones lybicus, and the gundi, Ctenodactylus vali) were investigated by means of light and transmission electron microscopy. In rodents, the Harderian gland consists of branching tubules, lined by a single layer of epithelial cells and possessing myoepithelial cells within their basal lamina. The Harderian gland contains porphyrins, stored as intraluminal masses. The glandular epithelium presents a single cell type (I) in Psammomys obesus, two cell types (I, II) in Ctenodactylus vali and the Wistar rat, and three cells types (I, II, III) in Gerbillus gerbillus, M. crassus, and M. lybicus. The type I and II cells are columnar, characterized by lipid vacuoles and well-developed profiles of the smooth endoplasmic reticulum. In Meriones and Gerbillus, the type I cell can be distinguished from the type II cell by cytoplasmic clefts. In Ctenodactylus vali, the type I cell is characterized by cytoplasmic rod-shaped crystalloid structures. These structures are also present in the sole cell type of Psammomys obesus. In the Wistar rat, the two cell types are distinguished by the number and the size of the lipid vacuoles. The content of the vacuole is released primarily by exocytosis, but holocrine and apocrine secretion was also noted. The type III cell is pyramidal, characterized by numerous mitochondria, and has an extraordinarily well-developed granular endoplasmic reticulum organized in concentric lamellae in Gerbillus gerbillus. The single excretory duct begins at the hilus. Mast cells, plasma cells, macrophages, fenestrated capillaries, and unmyelinated nerve endings with clear or dense-cored vesicles are present in the connective tissue. Melanocytes are predominant in the gland interstices of Psammomys obesus. The gland is surrounded by a thin connective tissue capsule, covered with the endothelium of the orbital venous sinus.

Immunohistochemical evidence for the presence of vasopressin in the rat harderian gland, retina and lacrimal gland.

The presence of vasopressin in the Harderian gland, the retina and the lacrimal gland of the rat, has been examined immunohistochemically. After fixation in Bouin's solution, immunostaining is accomplished with the peroxidase-antiperoxidase method. In the retina, the immunoreactive vasopressin is almost exclusively restricted to the ganglion cell layer. In the Harderian gland, the immunoreactivity is localized in the epithelial cells of the excretory duct and restricted to the cytoplasm. In the lacrimal gland, the immunoreactivity is localized in the secretory cells of the acini and the intercalated ducts and the immunostaining is restricted to the cytoplasm surrounding the nucleus. The possible functions of vasopressin in these ocular structures are discussed.

The harderian gland and its excretory duct in the Wistar rat. A histological and ultrastructural study.

The harderian gland in the Wistar rat consists of tubules with wide lumina lined by a single layer of columnar epithelial cells possessing myoepithelial cells within their basal laminae. The gland contains porphyrin pigment which is stored as solid intraluminal deposits. The glandular epithelium possesses 2 cell types, termed A and B. These are characterised by an extraordinarily well-developed tubular smooth endoplasmic reticulum and numerous lipid vacuoles. Type A cells can be distinguished from type B by the number, size and content of the lipid vacuoles. Type A cells are more numerous. They contain large lipid vacuoles with dense ribbon-like material identical in form to the material in the luminal masses of porphyrin pigment, whereas those of type B cells are small with crescentic dense lamellar material. The content of the vacuoles is essentially released by exocytosis, but holocrine secretion also occurs. The lipids and the ribbon-like material represent the bulk of the intraluminal secretory product. The secretion of porphyrins seems to be associated with type A cells. The single excretory duct is lined by a stratified epithelium. The duct epithelium comprises serous cell types, designated C1 and C2 and scarce mucus-secreting cells. Type C1 cells are characterised by numerous dense granules, whereas type C2 cells are distinguished by lysosomal structures. Fibroblasts, macrophages, mast cells, plasma cells, fenestrated capillaries and unmyelinated axons are frequently observed in the connective tissue. The gland is surrounded by a collagenous capsule and an outer layer of endothelial cells of the orbital venous sinus.

The harderian gland of desert rodents: a histological and ultrastructural study.

This study describes the structure of the harderian gland in desert rodents: 3 Gerbillidae species (Gerbillus gerbillus, Meriones crassus, Psammomys obesus) and 1 Ctenodactylidae species (Ctenodactylus vali). In all these species the gland consists of tubules lined by a single layer of epithelial cells and possesses myoepithelial cells within their basal laminae. The gland contains porphyrin which is stored as solid intraluminal deposits. The glandular epithelium presents a single cell type (type I) in Psammomys obesus, 2 cell types (I and II) in Ctenodactylus vali and 3 (I, II and III) in Gerbillus gerbillus and Meriones crassus. The type I and II cells are columnar. They are characterised by many lipid vacuoles and a well developed vesicle-like structure of smooth endoplasmic reticulum. In Gerbillus gerbillus and Meriones crassus the type I cells can be distinguished from type II cells by cytoplasmic clefts approximately 1 micron in length. In Ctenodactylus vali type I cells are characterised by cytoplasmic rod-shaped crystalloid structures approximately 0.5 microns in length which are frequently observed in the mitochondrial matrix. These structures are also present in the sole cell type of Psammomys obesus. Most of the secretory lipid vacuoles of the type I cell contain an electron-dense material, possibly porphyrin, which presents different appearances according to species: it is lamellar in Gerbillus gerbillus, trilamellar in Meriones crassus, and amorphous in Psammomys obesus and Ctenodactylus vali. Secretory lipid vacuoles are released primarily by exocytosis, but holocrine and apocrine secretion is also observed. The type III cells are pyramidal. This cell type is characterised by the presence of an extraordinarily well developed granular endoplasmic reticulum, organised in concentric lamellae in Gerbillus gerbillus, and very numerous mitochondria. Epithelial cells are frequently binucleate. The single excretory duct contains both mucous and serous cells. Mast cells, plasma cells, macrophages, fenestrated capillaries and unmyelinated nerve endings with clear or dense-cored vesicles are present in the connective tissue. Melanocytes are very numerous in the interstices of the Gerbillidae harderian gland. The gland is surrounded by a collagenous capsule and an outer layer of endothelial cells derived from the orbital venous sinus.